The present invention relates to the manufacture of data storage disks.
Optical data storage disks have gained widespread acceptance for the storage, distribution and retrieval of large volumes of information. Optical data storage disks, for instance, include audio CD (compact disc), CD-R (CD-recordable), CD-ROM (CD-read only memory), DVD (digital versatile disk or digital video disk) media, DVD-RAM (DVD-random access memory), and various types of rewritable media, such as magneto-optical (MO) disks and phase change optical disks.
Optical data storage disks can be produced by first making a master disk that has a surface pattern that represents encoded data on the master disk surface. The surface pattern, for instance, may be a collection of grooves that define master pits and master lands. The master disk is typically created by a relatively expensive mastering process.
After creating a suitable master, that master can then be used to make a stamper. The stamper has a surface pattern that is the inverse of the surface pattern encoded on the master. The stamper, then, can be used to stamp large quantities of replica disks, for example, in a mass production stamping process such as an injection molding process or a rolling bead process. Each replica disk may contain the data and tracking information that was encoded on the master.
During a stamping process, an inverse of the surface pattern on the stamper becomes molded into each replica disk, forming a collection of grooves that define lower reflectance xe2x80x9cpitsxe2x80x9d within a plane of higher reflectance xe2x80x9clands.xe2x80x9d Typically, the stamped side of the disk is then coated with a reflectance layer, such as a thin layer of aluminum, and in the case of a CD, followed by a protective layer of lacquer. Data tracks on an optical disk can be arranged in a spiral manner originating at the disk center and ending at the disk outer edge, or alternatively, a spiral track can originate at the disk outer edge and end at the disk center. The data also can lie in a series of concentric tracks spaced radially from the disk center.
Several thousand, e.g., typically about 50,000, replica disk substrates may be made using the same stamper. However, as a result of the pressure and temperature cycling involved in the molding process, stampers can become damaged and may deteriorate over time. Because the cost of making a recorded master disk can be relatively high, mastering can be a significant percentage of the final optical data storage disk cost. Moreover, the process of making a stamper from a master may destroy the master disk.
In an attempt to reduce manufacturing costs and increase efficiency, processes have been developed to make multiple stampers from one master disk. A collection of stampers made from the same master is referred to as a xe2x80x9cfamilyxe2x80x9d of stampers. The process of making a family of stampers involves making a first generation stamper from the master. The first generation stamper is then used to make a second generation stamper. The same process may be repeated using the second generation stamper to make a third generation stamper. The three generations of stampers, for instance, comprise a three generation family.
The invention provides one or more methods for making stampers that are suitable for stamping replica data storage disks. In one embodiment, the invention provides a method that includes determining desired groove depths and creating at least one stamper from a master disk. The stamper may have stamper groove depths substantially equivalent to the desired groove depths. However, the stamper groove depths may be substantially nonequivalent to groove depths of the master disk. In addition, groove widths of the stamper may be substantially equivalent to groove widths of the master disk.
The master disk may be created or obtained from a supplier. The method also may include determining desired groove depths for a replica disk. For instance, the groove depths of a particular replica disk may be measured to determine desired groove depths.
Creating a stamper may comprise creating a multi-generation family of stampers, at least one generation in the family having stamper groove depths substantially equivalent to the desired groove depths. For instance, the family may include one or more metal stampers and one or more plastic stampers. The groove depths of higher generation stampers may be systematically reduced by creating plastic stampers in preceding generations.
For example, a fifth generation stamper may exhibit groove depths that are substantially less than the groove depths of a second generation stamper. Photopolymer shrinkage in the plastic stampers, for instance, may reduce groove depths. A surface pattern with reduced groove depth may then be passed on from a plastic stamper to higher generation stampers created from the plastic stamper. In one embodiment, for example, a groove depth reduction for each generation of the family of stampers is determined and a number of the generations sufficient for the stamper groove depth to substantially equal the desired groove depth is determined. After creating one or more stampers, the stampers may be used to stamp a replica disk.
In another embodiment, the invention provides a method that includes creating a family of stampers from a master. The family may include a plurality of different generation stampers. Again, the master may be either created or obtained from a supplier. The family of stampers may include at least one metal stamper and at least one plastic stamper such as a polymethylmethacrylate (PMMA) stamper. The stampers in each generation of the family of stampers may have stamper groove widths substantially equivalent to groove widths on the master disk. However, groove depths may be different in some of the different generations.
The method also may include analyzing at least some of the different generation stampers and determining a preferred generation stamper based on groove depths. For instance, analyzing at least some of the different generation stampers may comprise measuring groove depths of at least some of the different generation stampers. Alternatively, analyzing at least some of the different generation stampers may comprise measuring groove depths of replica disks stamped by at least some of the stampers respectively. Determining a preferred generation stamper based on groove depths may comprise determining a preferred generation stamper based on groove depths of the different generation stampers. Alternatively, determining a preferred generation stamper based on groove depths may comprise determining a preferred generation stamper based on groove depths of replica disks stamped by at least some of the different generation stampers respectively.
The preferred generation stamper may be a stamper having desired groove depths. The groove depths of the preferred generation stamper, for instance, may be substantially nonequivalent to the groove depths of the master. As mentioned, groove depths may be different in different generations. Moreover, the groove depths of higher generation stampers may be systematically reduced by creating plastic stampers in lower generations. After determining the preferred generation stamper, one or more additional preferred generation stampers may be created. Replica disks may then be stamped using the preferred generation stampers.
In yet another embodiment, a method includes creating at least one first generation stamper from a master disk, creating at least one second generation stamper from the first generation stamper, creating at least one third generation stamper from the second generation stamper, and creating at least one fourth generation stamper from the third generation stamper. Again, the master disk may be created or obtained from a supplier. The method may further comprise creating additional generations, e.g., at least one fifth generation stamper from the fourth generation stamper, at least one sixth generation stamper from the fifth generation stamper, at least one seventh generation stamper from the sixth generation stamper, at least one eighth generation stamper form the seventh generation stamper, at least one ninth generation stamper form the eighth generation stamper, at least one tenth generation stamper from the ninth generation stamper, and so forth. After creating a stamper, the stamper may be used to stamp replica disks.
Additional details of these and other embodiments are set forth in the accompanying drawings and the description below. Other features, objects and advantages will become apparent from the description and drawings, and from the claims.